Metal-oxygen batteries can provide large energy levels because the active material in the cathode (oxygen) can be provided indefinitely from air. Current metal-air batteries require a counter anion to capture the metal ions that are generated during discharge of the battery. An example of a common counter ion is hydroxide generated by reduction of a catholyte such as water. Another common catholyte is ammonium chloride. The batteries that employ these catholyte typically include a reservoir of the catholyte. The reservoir and catholyte increase the size and weight of the battery and accordingly decrease the energy density of the battery. As a result, there is a need for a metal-oxygen battery having a reduced energy density.